Virtual reality can be viewed as a computer-generated simulated environment in which a user has an apparent physical presence. A virtual reality experience can be generated in 3D and viewed with a head-mounted display (HMD), such as glasses or other wearable display device that has near-eye display panels as lenses to display a virtual reality environment, which replaces the actual environment. Augmented reality, however, provides that a user can still see through the display lenses of the glasses or other wearable display device to view the surrounding environment, yet also see images of virtual objects that are generated for display and appear as a part of the environment. Augmented reality can include any type of input such as audio and haptic inputs, as well as virtual images, graphics, and video that enhances or augments the environment that a user experiences. As emerging technologies, there are many challenges and design constraints with virtual and augmented reality, from generation of the virtual objects and images so that they appear realistic in a real environment, to developing the optics small and precise enough for implementation with a wearable display device.
A wearable display device, such as a head-mounted display (HMD), for virtual or augmented reality typically has cameras and an illumination source that generates infra-red (IR) or near-IR light, which is imaged by the cameras to determine device orientation, object positioning, and for system calibrations. As a portable type of device, a wearable display device is typically battery powered and an illumination source can utilize excessive amounts of power, particularly when a wide field of view is illuminated. Further, the cameras of a wearable display device are, for the most part, always on and can be a consistent drain of battery power. The power consumption of a camera is a direct function of the size of its imaging array, and a larger imaging array will draw more current and use more power than a smaller imaging array.